The animation above (available here as an mp4, and here on YouTube) shows 11.22 µm infrared imagery at 2.5-minute time steps (bottom) and 10-minute time steps (top) from Himawari-8 on 14 May 2015. Category 2 intensity Typhoon Dolphin is approaching Guam, seen at the left edge of both panels in the frame. The 2.5-minute imagery gives a much better indication of the quick rise and decay of overshooting tops (IR brightness temperatures of the storm tops approach -95º C!). A 10-minute time step cannot fully resolve the evolution of these features. The 2.5-minute time step also better captures the divergent flow (and outward-propagating gravity waves) at the top of the central dense overcast. No eye was yet apparent in the infrared imagery, or on DMSP SSMI 85 GHz microwave imagery.

A similar animation from the previous day, 13 May, is shown here: gif, mp4, YouTube. The better organization of the storm on 14 May is readily apparent.

How high are the clouds in the Central Dense Overcast (CDO)? Cloud Heights are available from CLAVR-x (Clouds from AVHRR Extended). Data from Geostationary Satellites are processed and are available to download here. Values from COMS-1 and from MTSAT-2 (displayed with McIDAS-V) suggest maximum cloud heights near 55,500 feet.

The MIMIC Total Precipitable Water (TPW) product, below, showed that Typhoon Dolphin was able to tap rich moisture from the Intertropical Convergence Zone (ITCZ) during the 13-14 May period; TPW values within the tropical cyclone circulation were often in the 60-65 mm or 2.5-2.6 inch range (darker red color enhancement).

Following a period of rapid intensification, Super Typhoon Noul reached Category 5 strength late in the day on 09 May 2015 (ADT plot) as it slowly approached the northern tip of the Philippine island of Luzon. The Japanese Meteorological Agency (JMA) positioned one of the Himawari-8 rapid-scan “target” areas over the tropical cyclone, providing images at 2.5-minute intervals; 0.5-km resolution 0.64 µm visible (Band 4) images (above; click image to play animation; also available as an MP4 movie file and YouTube Video) showed intricate mesovortices within the eye, as well as gravity waves propagating radially outward from the eyewall region.

Atmospheric Bores form in stable air and create horizontal cloud bands that propagate perpendicular to the along-band direction. The feature seen above in GOES-13 visible imagery formed in stable air south of a High Pressure system that pushed a backdoor cold front into New England (surface analyses). The southern edge of this bore was likely eroding as it became influenced by warmer less-stable air over with the Gulf Stream — the warm waters of the Gulf Stream were apparent in the toggle, below, of POES AVHRR 0.86 µm visible and 12.0 µm infrared imagery at 1055 UTC. The bore was apparently moving over the top of a shallow layer of sea fog that had formed in the colder waters north of the Gulf Stream.

A disorganized subtropical system (Invest Area 90L) located over the southwest Atlantic to the east of Georgia and north of the Bahamas has the potential to become the first named system of the 2015 Atlantic Tropical Season (if named as a subtropical storm, this would be Ana). Visible imagery, above, shows a low-level swirl that is separated from any convection. However, during the 6 hours of the animation, the low-level swirl moves westward, moving more closely to active convection over the Gulf Stream. [Update, 2100 UTC 7 May: later images in the visible animation, above, showed strong convection developing over the surface circulation; another visible image animation with ship reports can be seen here]

MetOp-A passed over the southeast United States just after 1500 UTC on 7 May. The ASCAT scatterometer data (below) show a well-defined low-level circulation (with most winds just below tropical storm force) south and east of the deepest convection off the South Carolina/Georgia coasts.

ASCAT winds from Metop-A and GOES-13 10.7 µm imagery, both near 1500 UTC on 7 May 2015; Surface observations from Fixed Buoys are also plotted (click to enlarge)

Suomi NPP overflew this system at 0700 UTC on 7 May, and imagery from the VIIRS Day/Night Band gave information that allowed a definitive estimate of the location of a low-level circulation. A comparison of the 0702 imagery, below, and the 1826 UTC imagery, following, shows changes in the organization and vertical structure of the developing system.

Suomi NPP 1.61 µm near-infrared imagery can be used during the day to identify cirrus clouds: ice particles absorb (and do not reflect) radiation in these near-infrared wavelengths, but water droplets reflect. Thus, ice clouds appear dark. In the visible, both water and ice clouds are bright. The toggle below shows the 1.61 and the Visible imagery from Suomi-NPP.

At 2006 UTC, the International Space Station’s RapidScat instrument provided surface scatterometer winds (below) that depicted the broad circulation of Invest AL90; the strongest winds were located farther away from the center of the feature.

08 May Update: Invest Area AL90 was upgraded to Subtropical Storm Ana by the National Hurricane Center around 02 UTC. A Terra MODIS 11.0 µm IR image at 0249 UTC is shown below, with overlays of the MSLP analysis, buoy reports, and RTMA surface winds.